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Message-Id: <E1H7Uqx-0003X0-0u@llonio.corp.google.com>
Date: Thu, 18 Jan 2007 02:50:43 -0800
From: Al Borchers <alb@...gle.com>
To: linux-kernel@...r.kernel.org
Subject: Re: kernel cmdline: root=/dev/sdb1,/dev/sda1 "fallback"?
Thomas Chmielewski wrote:
> These all unpleasant tasks could be avoided if it was possible to have a
> "fallback" device. For example, consider this hypothetical command line:
>
> root=/dev/sdb1,/dev/sda1
Here is a patch to do this, though it sounds like you might have other
solutions.
This patch is for 2.6.18.1--thanks to Ed Falk for updating my original
2.6.11 patch. If people are interested I can update and test this on
the current kernel. It was tested on 2.6.11.
Please CC me with any comments.
-- Al
diff -uprN linux-2.6.18.1/init/do_mounts.c comma_root/init/do_mounts.c
--- linux-2.6.18.1/init/do_mounts.c 2006-10-13 20:34:03.000000000 -0700
+++ comma_root/init/do_mounts.c 2006-11-17 16:22:14.000000000 -0800
@@ -280,8 +280,9 @@ static int __init do_mount_root(char *na
return 0;
}
-void __init mount_block_root(char *name, int flags)
+static int __init mount_block_root_try(char *name, int flags)
{
+ int err;
char *fs_names = __getname();
char *p;
char b[BDEVNAME_SIZE];
@@ -289,7 +290,7 @@ void __init mount_block_root(char *name,
get_fs_names(fs_names);
retry:
for (p = fs_names; *p; p += strlen(p)+1) {
- int err = do_mount_root(name, p, flags, root_mount_data);
+ err = do_mount_root(name, p, flags, root_mount_data);
switch (err) {
case 0:
goto out;
@@ -307,19 +308,33 @@ retry:
printk("VFS: Cannot open root device \"%s\" or %s\n",
root_device_name, b);
printk("Please append a correct \"root=\" boot option\n");
-
- panic("VFS: Unable to mount root fs on %s", b);
}
printk("No filesystem could mount root, tried: ");
for (p = fs_names; *p; p += strlen(p)+1)
printk(" %s", p);
printk("\n");
- panic("VFS: Unable to mount root fs on %s", __bdevname(ROOT_DEV, b));
+
+ err = -1;
out:
putname(fs_names);
+ return err;
}
-
+
+static inline void __init mount_block_root_fail(void)
+{
+ char b[BDEVNAME_SIZE];
+
+ panic("VFS: Unable to mount root fs on %s", __bdevname(ROOT_DEV, b));
+}
+
+void __init mount_block_root(char *name, int flags)
+{
+ if (mount_block_root_try(name, flags) != 0)
+ mount_block_root_fail();
+}
+
+
#ifdef CONFIG_ROOT_NFS
static int __init mount_nfs_root(void)
{
@@ -363,12 +378,12 @@ void __init change_floppy(char *fmt, ...
}
#endif
-void __init mount_root(void)
+static int __init mount_root_try(void)
{
#ifdef CONFIG_ROOT_NFS
if (MAJOR(ROOT_DEV) == UNNAMED_MAJOR) {
if (mount_nfs_root())
- return;
+ return 0;
printk(KERN_ERR "VFS: Unable to mount root fs via NFS, trying floppy.\n");
ROOT_DEV = Root_FD0;
@@ -387,7 +402,18 @@ void __init mount_root(void)
}
#endif
create_dev("/dev/root", ROOT_DEV);
- mount_block_root("/dev/root", root_mountflags);
+ return mount_block_root_try("/dev/root", root_mountflags);
+}
+
+static inline void __init mount_root_fail(void)
+{
+ mount_block_root_fail();
+}
+
+void __init mount_root(void)
+{
+ if (mount_root_try() != 0)
+ mount_root_fail();
}
/*
@@ -396,6 +422,7 @@ void __init mount_root(void)
void __init prepare_namespace(void)
{
int is_floppy;
+ char *p,*pnext;
if (root_delay) {
printk(KERN_INFO "Waiting %dsec before mounting root device...\n",
@@ -405,27 +432,36 @@ void __init prepare_namespace(void)
md_run_setup();
- if (saved_root_name[0]) {
- root_device_name = saved_root_name;
+ for (p=saved_root_name; p && *p; p=pnext) {
+ pnext = strchr(p, ',');
+ if (pnext)
+ *pnext++ = '\0';
+ root_device_name = p;
if (!strncmp(root_device_name, "mtd", 3)) {
mount_block_root(root_device_name, root_mountflags);
goto out;
}
ROOT_DEV = name_to_dev_t(root_device_name);
+ if (ROOT_DEV == (dev_t)0)
+ continue;
if (strncmp(root_device_name, "/dev/", 5) == 0)
root_device_name += 5;
- }
- is_floppy = MAJOR(ROOT_DEV) == FLOPPY_MAJOR;
+ is_floppy = MAJOR(ROOT_DEV) == FLOPPY_MAJOR;
- if (initrd_load())
- goto out;
+ if (initrd_load())
+ goto out;
- if (is_floppy && rd_doload && rd_load_disk(0))
- ROOT_DEV = Root_RAM0;
+ if (is_floppy && rd_doload && rd_load_disk(0))
+ ROOT_DEV = Root_RAM0;
- mount_root();
+ if (mount_root_try() == 0)
+ goto out;
+
+ }
+ mount_root_fail();
out:
+ sys_unlink("/initrd.image");
sys_mount(".", "/", NULL, MS_MOVE, NULL);
sys_chroot(".");
security_sb_post_mountroot();
diff -uprN linux-2.6.18.1/init/do_mounts_initrd.c comma_root/init/do_mounts_initrd.c
--- linux-2.6.18.1/init/do_mounts_initrd.c 2006-10-13 20:34:03.000000000 -0700
+++ comma_root/init/do_mounts_initrd.c 2006-11-17 15:45:18.000000000 -0800
@@ -113,11 +113,9 @@ int __init initrd_load(void)
* mounted in the normal path.
*/
if (rd_load_image("/initrd.image") && ROOT_DEV != Root_RAM0) {
- sys_unlink("/initrd.image");
handle_initrd();
return 1;
}
}
- sys_unlink("/initrd.image");
return 0;
}
-
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